Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$48.46	11.222%	$53.8982	$53.90	$53.90	$53.90
Purchase #2	$68.83	13.804%	$78.3313	$78.33	$78.35	$78.30
Purchase #3	$176.71	5.158%	$185.8247	$185.82	$185.80	$185.80
Purchase #4	$198.39	6.353%	$210.9937	$210.99	$211.00	$211.00
Purchase #5	$200.58	11.445%	$223.5364	$223.54	$223.55	$223.50
Purchase #6	$246.75	3.154%	$254.5325	$254.53	$254.55	$254.50
Purchase #7	$11.35	12.479%	$12.7664	$12.77	$12.75	$12.80
7 purchase totals =	$951.07		$1,019.8832	$1,019.88	$1,019.90	$1,019.80